U.S. patent application number 17/123693 was filed with the patent office on 2022-06-16 for toner having special surface features and method to make the same.
The applicant listed for this patent is LEXMARK INTERNATIONAL, INC.. Invention is credited to LIGIA AURA BEJAT, CORY NATHAN HAMMOND, BENJAMIN KEITH NEWMAN, JING X. SUN, QING ZHANG.
Application Number | 20220187724 17/123693 |
Document ID | / |
Family ID | 1000005311672 |
Filed Date | 2022-06-16 |
United States Patent
Application |
20220187724 |
Kind Code |
A1 |
SUN; JING X. ; et
al. |
June 16, 2022 |
TONER HAVING SPECIAL SURFACE FEATURES AND METHOD TO MAKE THE
SAME
Abstract
The present disclosure relates to a polyester chemically
produced toner composition including a core shell toner particle
having special surface features and method to make the same. The
special surface features on the outer surface of the core shell
toner particle are created by the incorporation of a specially
designed polymer latex having styrene and acrylate monomers into
the core or shell of the toner particle wherein the polymer latex
having styrene and acrylate monomers is tailored to be incompatible
with the polyester resin(s) found in the core or the shell of the
toner particle.
Inventors: |
SUN; JING X.; (LEXINGTON,
KY) ; ZHANG; QING; (LEXINGTON, KY) ; NEWMAN;
BENJAMIN KEITH; (LEXINGTON, KY) ; HAMMOND; CORY
NATHAN; (WINCHESTER, KY) ; BEJAT; LIGIA AURA;
(LEXINGTON, KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LEXMARK INTERNATIONAL, INC. |
LEXINGTON |
KY |
US |
|
|
Family ID: |
1000005311672 |
Appl. No.: |
17/123693 |
Filed: |
December 16, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08F 220/1804 20200201;
G03G 9/09 20130101; C08F 220/20 20130101; C08F 2/22 20130101; G03G
9/0825 20130101; G03G 9/0815 20130101; G03G 9/09364 20130101; G03G
9/09321 20130101; C08F 2/38 20130101; C08F 220/1812 20200201; C08F
220/281 20200201; G03G 9/09371 20130101; G03G 9/0806 20130101; C08F
212/08 20130101 |
International
Class: |
G03G 9/08 20060101
G03G009/08; G03G 9/093 20060101 G03G009/093; G03G 9/09 20060101
G03G009/09; C08F 212/08 20060101 C08F212/08; C08F 220/18 20060101
C08F220/18; C08F 220/20 20060101 C08F220/20; C08F 220/28 20060101
C08F220/28 |
Claims
1. A method for producing toner, comprising: combining and
agglomerating a first polymer emulsion with a colorant dispersion,
a release agent dispersion to form toner cores; adding a borax
coupling agent to the toner cores; combining and agglomerating a
second polymer emulsion and a polymer latex including a hydrophilic
monomer having one of a carboxyl (--COOH) functional group and a
hydroxyl (--OH) functional group and hydrophobic styrene and
acrylate monomers with the toner cores having the borax coupling
agent to form toner shells around the toner cores; and fusing the
aggregated toner cores and toner shells to form toner particles,
wherein the toner that is produced has special surface features on
its outer surface and the polymer latex is used to control the raw
toner charge and charge distribution of the toner.
2. The method of claim 1, wherein the hydrophobic acrylate monomer
is an alkyl acrylate.
3. The method of claim 2, where the alkyl acrylate monomer is
lauryl acrylate.
4. The method of claim 1, wherein the hydrophilic monomer having
one of a carboxyl (--COOH) functional group is beta-carboxyethyl
acrylate.
5. The method of claim 1, wherein the hydrophilic monomer having
one of a hydroxyl (--OH) functional groups is hydroxyethyl
methacrylate.
6. A method for producing toner, comprising: combining a first
polymer emulsion with a colorant dispersion and a release agent to
form toner cores; adjusting the pH of the combination of the first
polymer emulsion, the colorant dispersion, and the release agent
dispersion and the polymer latex to promote agglomeration of the
toner cores; once the toner cores reach a predetermined size,
adding a borax coupling agent to the toner cores; combining a
second polymer emulsion and a polymer latex including a hydrophilic
monomer having one of a carboxyl (--COOH) functional group and a
hydroxyl (--OH) functional group and hydrophobic styrene and
acrylate monomers dispersion with the toner cores having the borax
coupling agent and forming toner shells around the toner cores;
once a desired toner particle size is reached, adjusting the pH of
the mixture of aggregated toner cores and toner shells to prevent
additional particle growth; and fusing the aggregated toner cores
and toner shells to form toner particles.
7. The method of claim 6, wherein the hydrophobic acrylate monomer
is an alkyl acrylate.
8. The method of claim 7, where the alkyl acrylate monomer is
lauryl acrylate.
9. The method of claim 6, wherein the hydrophilic monomer having
one of a carboxyl (--COOH) functional group is beta-carboxyethyl
acrylate.
10. The method of claim 6, wherein the hydrophilic monomer having
one of a hydroxyl (--OH) functional groups is hydroxyethyl
methacrylate.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] None.
BACKGROUND
1. Field of the Disclosure
[0002] The present disclosure relates to a polyester chemically
produced toner composition including a core shell toner particle
having special features and method to make the same. The special
surface features on the outer surface of the core shell toner
particle are created by the incorporation of a specially designed
styrene acrylic latex into the core of shell of the toner particle
wherein the styrene acrylic latex is tailored to be incompatible
with the polyester resin(s) found in the core or shell of the toner
particle. The resulting toner particle has a similar narrow charge
distribution compared to toners having expensive extra particular
additives.
2. Description of the Related Art
[0003] Controlling the charge of toners used in both single
component development and dual component development
electrophotographic printing is a significant objective. It is
desirable that toners used in both single component development and
dual component development electrophotographic printing possess a
stable charge and narrow charge distribution throughout their
entire life. Toners possessing this narrow charge distribution will
maintain good chargeability, charge stability and charge
distribution. Toners having these desirable characteristics provide
many advantages in electrophotographic printing including better
process control, less contaminant of the parts of the
electrophotographic printer, reduced toner usage, reduced cost of
printing and improved print quality.
[0004] Toner charging can be dependent on the use of extra
particulate additives (EPAs) found on the surface of the toner.
EPAs are attached on the surface of the raw toner particle through
mechanical blending and maintained on this surface through Van der
Waals forces. The use of EPAs on the surface of the raw toner
particle improves the flowability of the toner particles and
maintains a desirable charge and charge range of the toner
particles. Moreover, to achieve this desired charge and a narrow
charge range for the toner particles, most toner formulations use a
plurality of different sized of EPAs in combination with EPAs
having a specially treated surface. The use of this EPA package
increases the total cost of toner in terms of the additional raw
material cost as well as the additional manufacturing costs to add
the EPA package to the outer surface of the toner particle. In
addition, it is desirable that the EPA package stay on the toner
surface through the end of life of the toner. If the EPAs dislodge
from the toner surface or become embedded below the toner surface,
the toner charge will not be maintained at the same level as when
the EPAs were located on the outer surface of the toner
particle.
[0005] Another method to control the charge of the toner is the use
of a charge control agent. Like the EPA package, charge control
agents are expensive and will increase the overall cost of the
toner. Additionally, introducing the charge control agent into the
chemically processed toner manufacturing process is limiting
because the charge control agent is not soluble in both aqueous and
monomer solutions and has difficulty forming aqueous emulsions.
Therefore, it would be desirable to control the toner base powder's
charge and charge distribution without the use of expensive charge
control agents and multiple EPAs. Meanwhile, controlling the charge
distribution of the raw toner particles will result in a uniform
charge distribution which benefits toner usage, print quality and
print uniformity.
SUMMARY
Brief Description of the Drawings
[0006] The accompanying drawings incorporated in and forming a part
of the specification illustrate several aspects of the present
disclosure and together with the description serve to explain the
principles of the present disclosure.
[0007] FIG. 1 is a scanning electron image, in accordance with the
prior art, of a core shell toner particle having no special surface
features.
[0008] FIG. 2 is a scanning electron image, in accordance with the
prior art, of a multi-layered core shell toner particle having no
special surface features.
[0009] FIGS. 3-7 are scanning electron images, in accordance with
the present disclosure showing representative core shell toner
particles having special surface features.
[0010] FIG. 8 is a scanning electron image, in accordance with the
present disclosure showing representative multi-layered core shell
toner particle having special surface features.
[0011] FIG. 9 is a scanning electron image, in accordance with the
present disclosure showing representative multi-layered core shell
toner particle having special surface features.
[0012] FIG. 10 is a graph comparing the charge and charge
distribution of a commercially available core shell toner,
according to the prior art, to multi-layered core shell toners
having toner particles with special surface features, according to
the present disclosure.
DETAILED DESCRIPTION
[0013] Toner particles charge when a material-dependent electric
field is created at the surface of the toner particles. Therefore,
it is believed that the selection of materials used in the toner
formulation may have an influence on the toner surface charge.
Moreover, the electron donating/accepting ability difference
between the toner and carrier material may have the power to
determine the toner charge. Accordingly, raw toner may have the
ability to control its own charge. If the base toner charge can be
controlled by the toner formulation or process, then the raw toner
charge can be modified to an acceptable range and maintained at
this level throughout the life of the toner with or without the aid
of expensive EPAs and charge control agents. Meanwhile, controlling
the charge distribution of the raw toner particles will result in a
uniform charge Q/D which benefits toner usage, print quality and
print uniformity.
[0014] A specially designed polymer latex having styrene and
acrylate monomers can be used as an additive to act like a charge
control agent in the core or the shell of the toner particle
wherein the raw toner's charge and charge distribution can be
modified. The compatibility of the styrene-acrylate latex with the
polyester resins found in the core and or the shell can be
tailored. The compatibility or degree of interaction of the styrene
acrylate latex when mixed with the polyester resins in the core or
the shell of the toner particle can be controlled by designing a
specific styrene acrylic latex. The specially designed styrene
acrylic latex is achieved though the selection of 1.) the monomer
for the styrene acrylate latex, 2.) the degree of cross-linking,
3.) the molecular chain length, 4.) the glass transition
temperature (`Tg`), and 5.) the quantity and the position of the
styrene acrylic latex in the toner particle. This styrene acrylate
latex must have certain interactions with the polyester resin so
that the styrene acrylic latex and the polyester can be mixed and
agglomerated together in an emulsion aggregation toner making
process. Additionally, it is desirable that the styrene acrylate
latex also maintain its own nano-sized domains in the toner
particles.
[0015] Surprisingly, the addition of this specially designed
styrene acrylic latex into the toner's core or shell changes the
surface of the toner particle from a smooth surface to a gritted
surface having bumps or protuberances projecting out beyond the
surface of the toner particle. These protuberances on the surface
of the toner particle are created by controlling the interaction of
different polymers, i.e., styrene acrylate and polyester, used in
the toner formulation. The toner particle changes from a smooth to
a gritted or bumped surface having protuberances on the outer
surface of the toner particle. The protuberances appear due to the
migration of the self-agglomerated specially designed styrene
acrylate latex in the toner particle to the outer surface of the
toner particle when the toner is manufactured. Importantly, the
specially designed styrene acrylate latex maintains its own
nano-sized domains in the toner particles. To form this special
surface structure on the outer surface of a toner particle, the
less compatible this styrene acrylate latex is with the polyester
resin is preferred.
[0016] Specific properties of the styrene acrylate latex are chosen
to make the interaction between the styrene acrylate latex to be as
incompatible as possible with the polyester resin. As set forth
above, these specific properties include the monomer selection, the
quantity of the cross-linking agent, the chain transfer agent and
the surfactant, the molecular chain length, the glass transition
temperature and the quantity of the styrene acrylate latex used in
the toner formulation.
[0017] The specially designed styrene acrylate latex of the present
invention is formed from different type of monomers. Hydrophobic
monomers may be selected from a group including, but not limited
to, styrene, butyl acrylate, lauryl acrylate. Hydrophobic refers to
a relatively non-polar type chemical structure that tends to
self-associate in the presence of water. Lauryl acrylate or butyl
acrylate is used with styrene in the study. Although longer chain
length hydrocarbons are preferred for the interaction of the
monomer with the wax in the toner, the longer the hydrocarbon
chain, the less efficient the monomer is in co-polymerization and
more compatible with toner wax. Hydrophilic monomers may be
selected from carboxy (--COOH) and hydroxy (--OH) functional
groups. The hydrophilic monomers also affect the agglomeration of
the toner particle in the emulsion aggregation CPT process.
Hydrophilic functionality refers to relatively polar functionality
(e.g., a hydrogen bonding group) which may then tend to associate
with water molecules. Hydrophilic monomers provide additional
stability for the latex particles apart from that already provided
by the surfactant and initiator, and compatibility of styrene
acrylate latex with the polyester resin. Examples of hydrophilic
monomers are hydroxyethyl methacrylate, beta-carboxyethyl acrylate.
Furthermore, the quantity of the carboxy and hydroxyl functional
groups in the chosen hydrophilic monomers have been found to have a
great influence on the print quality and stability of the
toner.
[0018] The Tg of the styrene acrylate latex is controlled by the
monomer ratio, the cross-linking and chain transfer agents. The
preferred Tg of the styrene acrylate latex when used in the core is
between about 20.degree. C. to about 60.degree. C., preferably
about 40.degree. C. to maintain the hardness of the latex. The
preferred Tg of the styrene acrylic latex when used in the shell is
about 40.degree. C. to 60.degree. C., preferably 50.degree. C.
[0019] The quantity of the styrene acrylate latex to be used in the
core is about 15%-35 wt %, preferably 20%. The quantity of the
styrene acrylate latex to be used in the shell is about 0.5%-2 wt
%, preferably 1%.
[0020] The cross-linking agent controls the gel content of the
latex which, in turn, affects both fusing temperature and the
migration of the latex polymers. A relatively high cross-linking
the low molecular weight polymer chain is a preferable when
considering its compatibility with the polyester resins. In an
embodiment, divinyl benzene is useful as a cross-linking agent.
Other useful cross-linking agents include any kind of di- or
multifunctional meth(acrylate). The quantity of the cross-linking
agent to be used in the styrene acrylic latex is about 1.0% to
about 2%.
[0021] The chain transfer agent not only controls the molecular
weight of the latex, but also affects the grit formation of the
latex reaction. Generally, any kind of thiol compounds can be a
possible chain transfer agent. In the present latex making process,
two chain transfer agents are used: 1-dodecanethiol and
isooctyl-3-mercaptopropionate. The quantity of the chain transfer
agent to be used in the styrene acrylic latex is preferred to be
about 1.5% to about 3.5%. The quantity of the chain transfer agent
as well as the cross-linking agent influences the migration of the
styrene acrylic latex in the toner particle, especially when the
styrene acrylic latex is used in the core of the toner
particle.
[0022] Ammonium persulfate (0.1-0.5% wt) is used in the initiator
solution and a surfactant such as AKYPO-M100 (1 to 3% wt) is used
together with the organic portion and seed to control the latex
particle size around 100 nm. AKYPO-M100 is available from Kao
Corporation, Bunka Sumida-ku, Tokyo, Japan.
[0023] Example polyester binder(s) to be used in the core and the
shell are selected from commercially available resins using acid
monomers such as terephthalic acid, trimellitic anhydride,
dodecenyl succinic anhydride and fumaric acid. Further, the
polyester binder(s) may be formed using alcohol monomers such as
ethoxylated and/or propoxylated bisphenol A. Example polyester
resins include, but are not limited to, T100, TF-104, NE-1582,
NE-701, NE-2141, NE-1569, Binder C, FPESL-2, W-85N, TL-17,
TPESL-10, TPESL-11 polyester resins from Kao Corporation, Bunka
Sumida-ku, Tokyo, Japan, or mixtures thereof and various
commercially available crystalline polyester resin emulsions
available from Kao Corporation, Bunka Sumida-ku, Tokyo, Japan and
Reichhold Chemical Company, Durham, N.C. under the trade names EPC
2-20, EPC 3-20, 6-20, 7-20, CPES B1, EPC 8-20, EPC 9-20, EPC-10-20,
CPES B20 and CPES B25.
[0024] Colorants are compositions that impart color or other visual
effects to the toner and may include carbon black, dyes (which may
be soluble in a given medium and capable of precipitation),
pigments (which may be insoluble in a given medium) or a
combination of the two. A colorant dispersion may be prepared by
mixing the pigment in water with a dispersant. Alternatively, a
self-dispersing colorant may be used thereby permitting omission of
the dispersant. The colorant may be present in the dispersion at a
level of about 5% to about 40% by weight including all values and
increments therebetween. For example, the colorant may be present
in the dispersion at a level of about 10% to about 15% by weight.
The dispersion of colorant may contain particles at a size of about
50 nanometers (nm) to about 500 nm including all values and
increments therebetween. Further, the colorant dispersion may have
a pigment weight percent divided by dispersant weight percent (P/D
ratio) of about 1:1 to about 8:1 including all values and
increments therebetween, such as about 2:1 to about 5:1. The
colorant may be present at less than or equal to about 15% by
weight of the final toner formulation including all values and
increments therebetween.
[0025] The optional coupling agent used herein is borax (also known
as sodium borate, sodium tetraborate, or disodium tetraborate). As
used herein, the term borax coupling agent is defined as enabling
the formation of hydrogen bonds between polymer chains which
assists in the anchoring or binding of the polymer found in the
shell onto the surface of the toner core containing the polymers or
mixture of polymers, thereby helping to couple the shell to the
outer surface of the toner core. The borax coupling agent bonds the
shell to the outer surface of the core by forming hydrogen bonding
between its hydroxyl groups and the functional groups present in
the polymers utilized in the inventive toner formulation.
[0026] Typically, coupling agents have multivalent bonding ability.
Borax differs from commonly used permanent coupling agents, such as
multivalent metal ions (e.g., aluminum and zinc), in that its
bonding is reversible. In the electrophotographic process, toner is
preferred to have a low fusing temperature to save energy and a low
melt viscosity ("soft") to permit high speed printing at low fusing
temperatures. However, in order to maintain the stability of the
toner during shipping and storage and to prevent filming of the
printer components, toner is preferred to be "harder" at
temperatures below the fusing temperature. Borax provides
cross-linking through hydrogen bonding between its hydroxy groups
and the functional groups of the molecules it is bonded to. The
hydrogen bonding is sensitive to temperature and pressure and is
not a stable and permanent bond. For example, when the temperature
is increased to a certain degree or stress is applied to the
polymer, the bond will partially or completely break causing the
polymer to "flow" or tear off. The reversibility of the bonds
formed by the borax coupling agent is particularly useful in toner
because it permits a "soft" toner at the fusing temperature but a
"hard" toner at the storage temperature.
[0027] The wax used may include any compound that facilitates the
release of toner from a component in an electrophotographic printer
(e.g., release from a roller surface). The term `release agent` can
also be used to describe a compound that facilitates the release of
toner from a component in an electrophotographic printer. For
example, the release agent or wax may include polyolefin wax, ester
wax, polyester wax, polyethylene wax, metal salts of fatty acids,
fatty acid esters, partially saponified fatty acid esters, higher
fatty acid esters, higher alcohols, paraffin wax, carnauba wax,
amide waxes and polyhydric alcohol esters or mixtures thereof.
[0028] The wax or release agent may therefore include a low
molecular weight hydrocarbon based polymer (e.g., Mn.ltoreq.10,000)
having a melting point of less than about 140.degree. C. including
all values and increments between about 50.degree. C. and about
140.degree. C. The wax may be present in the dispersion at an
amount of about 5% to about 35% by weight including all values and
increments there between. For example, the wax may be present in
the dispersion at an amount of about 10% to about 18% by weight.
The wax dispersion may also contain particles at a size of about 50
nm to about 1 .mu.m including all values and increments there
between. In addition, the wax dispersion may be further
characterized as having a wax weight percent divided by dispersant
weight percent (RA/D ratio) of about 1:1 to about 30:1. For
example, the RA/D ratio may be about 3:1 to about 8:1. The wax is
provided in the range of about 2% to about 20% by weight of the
final toner formulation including all values and increments there
between. Exemplary waxes having these above enumerated
characteristics include, but are not limited to, SD-A01, SD-B01,
MPA-A02, CM-A01 and CM-B01 from Cytech Products, Inc., Polywax M70,
Polywax M80 and Polywax 500 from Baker Petrolite and WE5 from
Nippon Oil and Fat.
[0029] A surfactant, a polymeric dispersant or a combination
thereof may be used. The polymeric dispersant may generally include
three components, namely, a hydrophilic component, a hydrophobic
component and a protective colloid component. Reference to
hydrophobic refers to a relatively non-polar type chemical
structure that tends to self-associate in the presence of water.
The hydrophobic component of the polymeric dispersant may include
electron-rich functional groups or long chain hydrocarbons. Such
functional groups are known to exhibit strong interaction and/or
adsorption properties with respect to particle surfaces such as the
colorant and the polyester binder resin of the polyester resin
emulsion. Hydrophilic functionality refers to relatively polar
functionality (e.g., an anionic group) which may then tend to
associate with water molecules. The protective colloid component
includes water soluble group with no ionic function. The protective
colloid component of the polymeric dispersant provides extra
stability in addition to the hydrophilic component in an aqueous
system. Use of the protective colloid component substantially
reduces the amount of the ionic monomer segment or the hydrophilic
component in the polymeric dispersant. Further, the protective
colloid component stabilizes the polymeric dispersant in lower
acidic media. The protective colloid component generally includes
polyethylene glycol (PEG) groups. The dispersant employed herein
may include the dispersants disclosed in U.S. Pat. Nos. 6,991,884
and 5,714,538, which are assigned to the assignee of the present
application and are incorporated by reference herein in their
entirety.
[0030] The surfactant, as used herein, may be a conventional
surfactant known in the art for dispersing non self-dispersing
colorants and release agents employed for preparing toner
formulations for electrophotography. Commercial surfactants such as
the AKYPO series of carboxylic acids from AKYPO from Kao
Corporation, Bunka Sumida-ku, Tokyo, Japan may be used. For
example, alkyl ether carboxylates and alkyl ether sulfates,
preferably lauryl ether carboxylates and lauryl ether sulfates,
respectively, may be used. One particular suitable anionic
surfactant is AKYPO RLM-100 available from Kao Corporation, Bunka
Sumida-ku, Tokyo, Japan, which is laureth-11 carboxylic acid
thereby providing anionic carboxylate functionality. Other anionic
surfactants contemplated herein include alkyl phosphates, alkyl
sulfonates and alkyl benzene sulfonates. Sulfonic acid containing
polymers or surfactants may also be employed.
[0031] The following examples are provided to further illustrate
the teachings of the present disclosure, not to limit the scope of
the present disclosure.
[0032] Example Polyester Resin Emulsions
[0033] Preparation of Example Polyester Resin Emulsion A Having a
Medium Tg and Medium Tm
[0034] A polyester resin having a peak molecular weight of about
11,000, a glass transition temperature (Tg) of about 55.degree. C.
to about 58.degree. C., a melt temperature (Tm) of about
115.degree. C., and an acid value of about 8 to about 13 was used.
The glass transition temperature is measured by differential
scanning calorimetry (DSC), wherein, in this case, the onset of the
shift in baseline (heat capacity) thereby indicates that the Tg may
occur at about 55.degree. C. to about 58.degree. C. at a heating
rate of about 5.degree. C. per minute. The acid value may be due to
the presence of one or more free carboxylic acid functionalities
(--COOH) in the polyester. Acid value refers to the mass of
potassium hydroxide (KOH) in milligrams that is required to
neutralize one gram of the polyester. The acid value is therefore a
measure of the amount of carboxylic acid groups in the
polyester.
[0035] 150 g of the polyester resin was dissolved in 450 g of
methyl ethyl ketone (MEK) in a round bottom flask with stirring.
The dissolved resin was then poured into a beaker. The beaker was
placed in an ice bath directly under a homogenizer. The homogenizer
was turned on at high shear and 3.7 g of 10% potassium hydroxide
(KOH) solution and 500 g of de-ionized water were immediately added
to the beaker. The homogenizer was run at high shear for about 2-4
minutes then the homogenized resin solution was placed in a vacuum
distillation reactor. The reactor temperature was maintained at
about 43.degree. C. and the pressure was maintained between about
22 inHg and about 23 inHg. About 500 mL of additional de-ionized
water was added to the reactor and the temperature was gradually
increased to about 70.degree. C. to ensure that substantially all
of the MEK was distilled out. The heat to the reactor was then
turned off and the mixture was stirred until it reached room
temperature. Once the reactor reached room temperature, the vacuum
was turned off and the resin solution was removed and placed in
storage bottles.
[0036] The particle size of Polyester Resin Emulsion A was between
about 190 nm and about 240 nm (volume average) as measured by a
NANOTRAC Particle Size Analyzer. The pH of the resin solution was
between about 7.5 and about 8.2.
[0037] Example Polyester Resin Emulsion B Having a Low Tg and a Low
Tm
[0038] A polyester resin having a peak molecular weight of about
6500, a glass transition temperature of about 49.degree. C. to
about 54.degree. C., a melt temperature of about 95.degree. C., and
an acid value of about 21 to about 24 was used to form an emulsion
using the procedure outlined making Polyester Resin Emulsion A
except using about 12.8 g of the 10% potassium hydroxide (KOH)
solution.
[0039] The particle size of Polyester Resin Emulsion B was between
about 160 nm and about 220 nm (volume average) as measured by a
NANOTRAC Particle Size Analyzer. The pH of the resin solution was
between about 6.3 and about 6.8.
[0040] Preparation of Example Polyester Resin Emulsion C Having a
High Tg and a High Tm
[0041] A polyester resin having a peak molecular weight of about
13,000, a glass transition temperature of about 58.degree. C. to
about 62.degree. C., a melt temperature of about 110.degree. C. and
an acid value of about 20 to 23 was used to form an emulsion using
the procedure outlined making Polyester Resin Emulsion A except
using about 10 g of the 10% potassium hydroxide (KOH) solution.
[0042] The particle size of Polyester Resin Emulsion C was between
about 190 nm and about 240 nm (volume average) as measured by a
NANOTRAC Particle Size Analyzer. The pH of the resin solution was
between about 6.5 and about 7.0.
[0043] Preparation of Example Crystalline Polyester Resin
Emulsion
[0044] A crystalline polyester resin having a glass transition
temperature of about 82.degree. C. a melt temperature of about
82.degree. C., and an acid value of about 15 to about 18 was used
to form an emulsion.
[0045] 125 g of the crystalline polyester resin was dissolved in
375 g of tetrahydrofuran (THF) in a round bottom flask with heat
and stirring. The dissolved resin was then poured into a beaker.
The beaker was placed under a homogenizer. The homogenizer was
turned on at high shear and 17 g of 10% potassium hydroxide (KOH)
solution and 400 g of de-ionized water were immediately added to
the beaker. The homogenizer was run at high shear for about 2-4
minutes then the homogenized resin solution was placed in a vacuum
distillation reactor. The reactor temperature was maintained at
about 43.degree. C. and the pressure was maintained between about
22 inHg and about 23 inHg. About 500 mL of additional de-ionized
water was added to the reactor and the temperature was gradually
increased to about 60.degree. C. to ensure that substantially all
of the THF was distilled out. The heat to the reactor was then
turned off and the mixture was stirred until it reached room
temperature. Once the reactor reached room temperature, the vacuum
was turned off and the resin solution was removed and placed in
storage bottles.
[0046] The particle size of the crystalline polyester resin
emulsion was between about 185 nm and about 235 nm (volume average)
as measured by a NANOTRAC Particle Size Analyzer. The pH of the
resin solution was about 8.6.
[0047] Preparation of Magenta Pigment Dispersion
[0048] About 10 g of AKYPO RLM-100 polyoxyethylene(10) lauryl ether
carboxylic acid from Kao Corporation, Bunka Sumida-ku, Tokyo, Japan
was combined with about 350 g of de-ionized water and the pH was
adjusted to .about.7-9 using sodium hydroxide. About 10 g of
Solsperse 27000 from Lubrizol Advanced Materials, Cleveland, Ohio,
USA was added and the dispersant and water mixture was blended with
an electrical stirrer followed by the relatively slow addition of
100 g of pigment red 122. Once the pigment was completely wetted
and dispersed, the mixture was added to a horizontal media mill to
reduce the particle size. The solution was processed in the media
mill until the particle size was about 200 nm. The final pigment
dispersion was set to contain about 20% to about 40% solids by
weight. The same method is applied to the preparation of the Cyan
Pigment Dispersion, except replacing pigment red 122 with pigment
blue 15:3.
[0049] Preparation of Example Wax Emulsion
[0050] About 12 g of AKYPO RLM-100 polyoxyethylene(10) lauryl ether
carboxylic acid from Kao Corporation, Bunka Sumida-ku, Tokyo, Japan
was combined with about 325 g of de-ionized water and the pH was
adjusted to .about.7-9 using sodium hydroxide. The mixture was then
processed through a microfluidizer and heated to about 90.degree.
C. About 60 g of ester/paraffin wax from Cytec Products Inc.,
Elizabethtown, Ky. was added to the hot mixture while the
temperature was maintained at about 90.degree. C. for about 15
minutes. The emulsion was then removed from the microfluidizer when
the particle size was below about 300 nm. The solution was then
stirred at room temperature. The wax emulsion was set to contain
about 10% to about 40% solids by weight.
[0051] General Procedure for the Preparation of the Styrene Acrylic
Latex to be Used in Core of Toner
[0052] In a flask, 380 g styrene, 170 g butyl acrylate, 17 g
.beta.-carboxyethyl acrylate, 1 g divinylbenzene, 9.25 g
1-dodecanethiol, 9.15 g isooctyl-3-mercaptopropionate were weighed
and mixed. This served as the organic portion of the reaction. From
the organic portion, 58.7 g was weighed out and used as seed.
[0053] The initiator solution is prepared in another flask with 109
g of deionized water, 0.44 g of Ammonium persulfate, 80 g of 15%
AKYPO-M100 with ammonium hydroxide neutralized.
[0054] In a 3 L four-neck, round-bottom flask equipped with a
thermocontroller, condenser, mechanical stirrer and nitrogen inlet,
about 1140 g deionized water, 40 g of AKYPO 15% surfactant with
Ammonium hydroxide were added and heated to 82.degree. C. At
82.degree. C., the organic seed with 0.33 g Ammonium persulfate
were added and the reaction mixture held for 25 minutes. The
organic and initiator portion were added drop-wise to the reactor
while maintaining the temperature at 82.degree. C. The addition
continued for approximately three to four hours. At approximately
five hours, 0.76 g of t-Butyl hydroperoxide (70%) and 0.51 g of
L-Ascorbic acid in 25 ml of deionized water (respectively) were
added separately to the reactor. The reaction was held for another
two hours and cooled down to room temperature. The product was
filtered through a mesh. The final particle size was about 100
nm.
[0055] Latexes 1-11 were produced using the procedure outlined in
the General Preparation of Latex above, except the different
quantity of ingredients as listed in Table 1 below.
TABLE-US-00001 TABLE 1 Styrene Acrylate Latex 1 2 3 4 5 6 7 8 9 10
11 Hydroxyethyl 17.44 methacrylate Styrene 345 345 327 380 371 412
396 395 400 397 384 Butyl Acrylate 210 204 229 169.7 180 137 159
159 157 157 165 Beta- Carboxyethyl 16.9 16.9 16.9 16.9 16.9 16.9
16.9 16.9 16.9 16.9 16.9 acrylate divinylbenzene 10.99 10.99 10.99
10.99 8.79 10.99 5.49 8.79 8.79 8.79 8.79 1-Dodecanethiol 6.16 9.25
6.17 9.25 9.25 9.25 7.71 7.71 6.17 7.71 7.71 Isooctyl 3- 6.1 9.15
6.1 9.15 9.15 9.15 7.63 7.63 6.1 7.63 7.63 mercaptopropionate
[0056] Preparation of Latexes 12 and 13 to be Used in the Shell of
the Toner
[0057] In flask A, 2-hydroxyethyl methacrylate 4.48 g,
.beta.-carboxyethyl acrylate 2.57 g, 1-Dodecanethiol 1.92 g,
Isooctyl-3-mercaptopropionate 1.90 g, styrene 100 g and butyl
acrylate 42 g were weighed and mixed.
[0058] In flask B, 0.4 g divinylbenzene and 12 g mixture from flask
A were mixed as seed.
[0059] In flask C, 0.4 g divinylbenzene and 90 g mixture from flask
A were mixed.
[0060] In flask D, 1.4 g divinylbenzene and the rest of the mixture
in flask A were mixed.
[0061] The initiator solution is prepared in flask E with 80 g of
deionized water, 0.3 g of ammonium persulfate, 8.5 g of 15% Akypo
solution and 3.0 g of ammonium hydroxide.
In a 3 L four-neck, round-bottom flask equipped with a
thermocontroller, condenser, mechanical stirrer and nitrogen inlet,
about 500 g deionized water, 1.6 g of Akypo surfactant and 1.6 g of
ammonium hydroxide were added and heated to 82.degree. C. At
82.degree. C., the mixture in flask B with 0.16 g ammonium
persulfate were added and held for 25 minutes. The mixture in flask
C and initiator solution in flask E were added drop-wise to the
reactor in a speed ratio of 3:1 while maintaining the temperature
at 82.degree. C. The addition continued for approximately 32 min.
until completion. Then the mixture in flask D was added at the same
speed. At approximately four hours, 0.19 g of t-butyl hydroperoxide
and 0.13 g of L-ascorbic acid in 25 ml of deionized water
(respectively) were added separately to the reactor. The reaction
was held for another two hours and cooled down to room temperature.
The product was filtered through a mesh. The final particle size
was around 100 nm. Latex 11 is used as additive in the toner shell
resin. Latex 12 was prepared using the same procedure as outlined
for the preparation of Latex 11, except 80 grams of mixture from
Flask A are used in Flask C.
[0062] Preparation of Toners
[0063] Control Toner 1
[0064] Components were added to a 2 L reactor in the following
amounts: about 150 g of polyester resin emulsion B of 29.75% wt,
391.61 g of 29.76% wt Example Polyester Resin Emulsion A, 52.74 g
of the Cyan Pigment Dispersion (with 29.10% wt solid and 5:1
Pigment-to-Dispersant ratio), 99.52 g of the 34.40% Example Wax
Emulsion with wax-to-dispersant ratio of about 28.5:1, and 834 g of
the deionized water.
[0065] The mixture was mixed in the reactor at about 25.degree. C.
and a circulation loop was started consisting of a high shear mixer
and an acid addition pump. The mixture was sent through the loop
and the high shear mixer was set at 10,000 rpm. Acid was slowly
added to the high shear mixer to evenly disperse the acid in the
toner mixture so that there were no pockets of low pH.
[0066] Acid addition took about 4 minutes with 210 g of 1% sulfuric
acid solution. The flow of the loop was then reversed to return the
toner mixture to the reactor and the temperature of the reactor was
increased to about 40-45.degree. C. Once the particle size reached
4.5 to 5.0 .mu.m (number average), 5% borax solution (20 g of
solution having 1.0 g borax) was added. After the addition of
borax, 290.16 g of Example Polyester Resin Emulsion C with 29.70%
wt solid was added. The mixture was stirred for about 5 minutes and
the pH was monitored. Slowly heat the mixture to about 54.degree.
C. Once the particle size reached 5.5 .mu.m (number average), 4%
NaOH was added to raise the pH to about 6.7 to stop the particle
growth. The reaction temperature was held for one hour. The
particle size was monitored during this time period. Once particle
growth stopped, the temperature was increased to 93.degree. C. to
cause the particles to coalesce. This temperature was maintained
until the particles reached their desired circularity (about
0.97-0.98). The toner was then washed and dried. The toner had a
volume average particle size of 6.77 .mu.m and a number average
particle size of 5.50 .mu.m. Fines (<2 .mu.m) were present at
0.14% (by number) and the toner possessed a circularity of
0.97.
[0067] Preparation of Toners 1-11
[0068] The preparation of Toners 1-11 followed the same procedure
as outlined for the Control Toner 1 except about 45 g (100%) of the
identified specially designed Styrene Acrylate Latex replaced the
Polyester Resin Emulsion B. Attributes of the different toners
tested are listed in Table 2 below. Latex glass transition
temperatures for Toners 1-11 were roughly calculated using a
monomers ratio calculation. The quantity of cross-linking agent and
chain transfer agents are based on the total monomers used by
weight. Toner ship/store are measure at 50 C. The presence of the
special surface structure was observed with a Scanning Electron
Microscope (SEM).
TABLE-US-00002 TABLE 2 Toner and Styrene Acrylic Latex Used in Core
1 2 3 4 5 6 7 8 9 10 11 Control 1 Latex Tg 27 21 23 29.6 27 42 35
36 37 37 43 Cross-Linking wt % 1.8 1.8 1.8 1.8 1.5 1.8 0.9 1.5 1.5
1.5 1.5 Chain transfer wt % 2 3 2 3 3 3 2.6 2.6 2 2.6 2.6 Toner
ship/store 57 126 59 86 114 64 89 88 62 58 54 55 special surface
structure yes not yes yes yes yes yes yes less yes less none (SEM)
clear
[0069] Preparation of Control Toner 2
[0070] In a 5 L reactor, about 244 g of Crystalline Polyester
Emulsion with 21.6% wt solid, 592.4 g of 29.76% wt Example
Polyester Resin Emulsion A, 34.3 g (100%) of Pigment Red 122 and 18
g Pigment Red 184 (100%) (dispersion with about 30% wt solid and
5:1 pigment-to-dispersant ratio), 210 g of the 34.0% Example Wax
Emulsion with wax-to-dispersant ratio of about 28.5:1, and 1600 g
of the deionized water.
[0071] The mixture was mixed in the reactor at about 25.degree. C.
and a circulation loop was started consisting of a high shear mixer
and an acid addition pump. The mixture was sent through the loop
and the high shear mixer was set at 10,000 rpm. Acid was slowly
added to the high shear mixer to evenly disperse the acid in the
toner mixture so that there were no pockets of low pH. Acid
addition took about 4 minutes with 170 g of 2% sulfuric acid
solution. The flow of the loop was then reversed to return the
toner mixture to the reactor and the temperature of the reactor was
increased to about 40.degree. C. Once the particle size reached 4.0
.mu.m (number average), 353 g of polyester resin emulsion A was
added (with 100 g water wash the container). Once the particle size
reached 4.7 um, 4% borax solution 21.3 g was added. After the
addition of borax, 605 g of Example Polyester Resin Emulsion C with
29.70% wt solid was added. The mixture was stirred for about 5
minutes and the pH was monitored. Once the particle size reached
5.5 .mu.m (number average), 4% NaOH was added to raise the pH to
about 7-7.4 to stop the particle growth. The reaction temperature
was held for one hour. The particle size was monitored during this
time. Once particle growth stopped, the temperature was increased
to 93.degree. C. to cause the particles to coalesce. This
temperature was maintained until the particles reached their
desired circularity. The toner was then washed and dried. The toner
had a volume average particle size of 5.96 .mu.m and a number
average particle size of 5.30 .mu.m. Fines (<2 .mu.m) were
present at 0.72% (by number) and the toner possessed a circularity
of 0.965.
[0072] Preparation of Toners 12 and 13 Having Styrene Acrylic Latex
in the Shell
[0073] Components were added to a 2 L reactor in the following
amounts: about 122 g of Crystalline Polyester Emulsion with 21.6%
wt solid, 296 g of 29.76% wt Example Polyester Resin Emulsion A,
17.1 g (100% wt) of PR122 and 8.9 g (100% wt) PR184 pigment
(dispersion about 30% wt solid and 5:1 pigment-to-dispersant
ratio), 105 g of the 34.0% Example Wax Emulsion with
wax-to-dispersant ratio of about 28.5:1, and 800 g of the deionized
water.
[0074] The mixture was mixed in the reactor at about 25.degree. C.
and a circulation loop was started consisting of a high shear mixer
and an acid addition pump. The mixture was sent through the loop
and the high shear mixer was set at 10,000 rpm. Acid was slowly
added to the high shear mixer to evenly disperse the acid in the
toner mixture so that there were no pockets of low pH. Acid
addition took about 4 minutes with 85 g of 2% sulfuric acid
solution. The flow of the loop was then reversed to return the
toner mixture to the reactor and the temperature of the reactor was
increased to about 40.degree. C. Once the particle size reached
3.5.0 .mu.m (number average), 176 g of polyester resin emulsion A
was added. Then, 252 g of Example Polyester Resin Emulsion C with
29.70% wt solid was added followed by 50 g of the emulsion C mixed
with 1% (wt of resin) of the Styrene Acrylate Latex 11 used as
additive in the shell. The mixture was stirred for about 5 minutes
and the pH was monitored. Once the particle size reached 5.5 .mu.m
(number average), 4% NaOH was added to raise the pH to about 7-7.4
to stop the particle growth. The reaction temperature was held for
one hour. The particle size was monitored during this time. Once
particle growth stopped, the temperature was increased to
83.degree. C. to cause the particles to coalesce. This temperature
was maintained until the particles reached their desired
circularity. The toner was then washed and dried. The toner had a
volume average particle size of 5.05 .mu.m and a number average
particle size of 4.43 .mu.m. Fines (<2 .mu.m) were present at
0.91% (by number) and the toner possessed a circularity of 0.979.
Toner 13 was made using the same procedure to make Toner 12, except
Styrene Acrylic Latex 13 was used as the additive in the shell. The
toner had a volume average particle size of 5.33 .mu.m and a number
average particle size of 4.56 .mu.m. Fines (<2 .mu.m) were
present at 0.21% (by number) and the toner possessed a circularity
of 0.98.
[0075] Tested attributes of the Toners 12 and 13 are listed in
Table 3 below. Latex glass transition temperatures were measured by
DSC. The quantity of cross-linking agent and chain transfer agents
are based on the total monomers used by weight. The presence of the
special surface structure was observed with Scanning Electron
Microscope (SEM). Latex 12 and Latex 13 varied in the core/shell
monomer ratio.
TABLE-US-00003 TABLE 3 Toner and Styrene Acrylic Latex Used in
Shell 12 13 Control 2 Latex Tg 42 40 Cross-Linking wt % 1.6 1.6
Chain transfer wt % 2.5 2.5 special surface structure yes yes none
(SEM)
[0076] Typically in the general CPT toner particle design, a
specific component of the toner is preferred to maintain in the
designed specific position in the toner particles. The migration of
the component to an undesired position in the toner particle is not
preferred and can result in a failure of the function. As shown in
FIGS. 3-7, the position of styrene acrylate latexes 1,2,3,7 and 8
in the core of the toner was not maintained as designed and
surprisingly migrated to the surface of the toner particle. This
phenomenon can be seen by the appearance of the protuberances on
the surface of the toner particle in FIGS. 3-9. It is believed that
the protuberances or the special surface structure were created
because the styrene acrylate has unique chemical, thermal and
mechanical properties compared to the polyester resins found in the
core and shell of the toner particle.
[0077] The incompatibility of the styrene acrylic latex and the
polyester resin used in the toner formulation plays an important
role for creating the special surface structure or protuberances on
the surface of the toner particle. Surprisingly the protuberances
function like EPAs and are created when the styrene acrylic latex
is tailored to be incompatible with the polyester resin found in
the core or shell of the toner. Additionally, it is important that
the styrene acrylic latex is maintained in its own nano sized
domains in the toner. To create the special surface structure when
the styrene acrylate latex is used in the core, lauryl acrylate is
not a good choice compared to butyl acrylate. A styrene acrylic
latex containing long chain hydrocarbon monomers such as lauryl
acrylate and octyltrimethoxysilane as well as the hydroxyethyl
methacrylate do not create the special surface structure when used
in the core because these long chain hydrocarbon monomers are too
compatible with either the polyester resins and/or with the wax
used in the core of the toner. As a result of this compatibility,
the styrene acrylate latex loses its own domain and is mixed with
the polyester resins and or wax found in the core.
[0078] FIG. 1 and FIG. 2 are SEMs of Control Toner 1 and Control
Toner 2 and show the toner particles in these two toners having a
very smooth surface. FIGS. 3-7 are SEMs of Toners 1,2,3,7 and 8
wherein the specially designed styrene acrylate latex is added in
the core of the toner particle. The only difference between the
formulation for Toners 1,2 3,7 and 8 and Control Toner 1 is the
addition of the specially designed styrene acrylic latex in the
core. As can be seen from FIGS. 3-7, the surface of the toner
particles has a grit-like surface or protuberances on the surface
of the toner particle in Toners 1,2,3,7, and 8. These protuberances
occur on the surface of the toner particle due to the migration of
the specially designed styrene acrylic latexes 1,2,3,7 and 8 onto
the surface of the toner particle.
[0079] FIGS. 8 and 9 are SEMs of toner particles in Toners 11 and
12 wherein the specially designed styrene acrylic latex is added to
the shell. The only difference between the formulation of Toners 11
and 12 and Control Toner 2 is the addition of the specially
designed styrene acrylic latexes 11 and 12 into the toner shell. As
can be seen from FIGS. 8 and 9, the surface of the toner particles
has a grit-like surface or protuberances on the surface of the
toner particle in Toners 11 and 12. These protuberances occur on
the surface of the toner particle due to the migration of the
specially designed styrene acrylic latexes 11 and 12 onto the
surface of the toner particle.
[0080] The addition of the specially designed styrene acrylate
latexes 12 and 13 into the shell of Toners 12 and 13 can be used to
control the raw toner charge and charge distribution of the toners.
FIG. 10 compares the charge and charge distribution of Xerox.RTM.
Super EA Eco toner to Toners 12 and 13. Toners 12 and 13 have the
specially designed styrene acrylate latexes 12 and 13 as an
additive in their respective toner shells. As can be seen in FIG.
10, the raw toner charge and charge distribution of Toners 12 and
13 are similar to the raw toner charge and charge distribution of
Xerox.RTM. Super EA Eco toner treated with expensive EPAs. FIGS. 8
and 9 show Toners 12 and 13 having the special surface structure
containing protuberances located on the surface of the toner
particle. These protuberances provide a strong and special electron
donating/accepting capability compared to Control Toner 2 having
only a polyester resin in its shell, which in turn narrows the
charge distribution of Toners 12 and 13. Accordingly, it is
possible to utilize the specially designed styrene acrylate latex's
incompatibility with polyester resin and the surprising migration
of this specially designed styrene acrylic latex to the surface of
the toner particle to control the raw toner charge and charge
distribution. Moreover, by creating this gritted surface having
protuberances on the surface of the toner particle, the raw toner
or base powder can maintain a narrow charge without the use of
charge control agents and or expensive EPAs. This is especially
important because later in the life of the toner, EPAs are dropped
out or become dislodged from the surface of the toner. Having a
toner not dependent of the use of EPAs ultimately benefits the
toner usage and energy minimization (TEC' or typical energy
consumption) in EP printing.
* * * * *